In recent years, DVDs have gained widespread acceptance as optical discs permitting the recording of moving picture images in the form of digital information. In addition, Blu-ray discs (hereinafter called “BD” for short), which are known as the next-generation optical discs capable of recording at even higher densities than DVDs, already have reached the deployment stage.
In case of DVDs, BDs and other optical discs, the minimum unit of logical access is called a sector. In the past, when a DVD-RAM or a BD had sectors where information could not be recorded or reproduced (called “defective sectors”), the reliability of recording data was ensured by performing the so-called defect management, whereby ECC blocks (in case of a DVD) or clusters (in case of a BD) in good condition were substituted for ECC blocks or clusters containing defective sectors. Defective sectors are generated not only during disc manufacture, but also as a result of scratches, contamination, and the like, adhering to the surface of discs when discs are in use.
An example of a conventional optical disc where such defect management is performed, as well as an apparatus for its recording and reproduction, are disclosed in Patent Document 1. Here, explanations will be provided regarding the conventional optical disc (DVD) disclosed in Patent Document 1.
As shown in FIG. 11, a conventional optical disc 91 has a data recording area 95 and disc information areas 94. Parameters necessary for accessing the disc 91 are stored in the disc information areas 94. In this example, the disc information areas 94 are provided both on the innermost peripheral side and on the outermost peripheral side of the disc 91. The disc information area 94 on the innermost peripheral side is called the lead-in (lead-in) area. The disc information area 94 on the outermost peripheral side is called the lead-out (lead-out) area.
The recording and reproduction of data is performed in the data recording area 95. An absolute address called a physical sector number (hereinafter called PSN for short) is allocated in advance to each of the sectors of the data recording area 95.
A higher level control device (typically a host computer) issues an instruction for recording or reproduction to an optical disc device in sector units. When an instruction is issued by the higher-level control device to perform reproduction of a certain sector, the optical disc device reproduces the ECC block containing the sector from the disc and performs error correction, after which it sends back only the portion of the data that corresponds to the designated sector. In addition, when an instruction is issued by the higher-level control device to perform recording in a certain sector, the optical disc device reproduces the ECC block containing the sector from the disc and performs error correction, after which it substitutes recording data obtained from the higher-level control device for the portion of the data corresponding to the designated sector, re-calculates and re-assigns an error correction code to the ECC block, and records the ECC block containing the sector on the disc. This type of recording operation is called “read-modified write”
The data recording area 95 contains a volume space 96 and a spare area 97. The volume space 96, which is an area intended for storage of user data, contains a logical volume space 96a and volume structures 96b showing the structure of the logical volume space 96a. To provide access to the volume space 96, logical sector numbers (hereinafter called LSNs for short) are allocated to the sectors contained in the volume space 96. Data recording and reproduction is performed by accessing sectors on the disc 91 using the LSNs.
The spare area 97 contains at least one sector (substitute sector) that can be used in place of a defective sector when a defective sector is generated in the volume space 96.
The disc information areas 94 each contain a control data area 94a and a defect management information area 94b. Defect management information 100, which is used for managing defective sectors, is stored within the defect management information area 94b. 
The defect management information 100 includes a disc definition structure 110, a primary defect list (hereinafter called PDL for short) 120, and a secondary defect list (hereinafter called SDL for short) 130.
The PDL 120 is used to manage defective sectors detected during inspection prior to shipment of the disc 91. The pre-shipment inspection of the disc 91 usually is performed by the manufacturer of the disc 91. The SDL 130 is used to manage defective sectors detected when a user uses the disc 91.
FIG. 12 shows the structure of the SDL 130. The SDL 130 contains a secondary defect list header (SDL header) 200 containing an identifier identifying it as an SDL, information (SDL entry number information) 210 showing the number of SDL entries 220 registered in the SDL, and one or more SDL entries 220 (in the example shown in FIG. 12, entry 1 through entry m). Note that a value of zero in the SDL entry number information 210 shows that there are no defective sectors registered in the SDL.
FIG. 13 shows the structure of an SDL entry 220. An SDL entry 220 contains a status field 220a, a field 220b for storing information describing the location of defective sectors, and a field 220c used for storing information describing the location of substitute sectors substituted for defective sectors.
The status field 220a is used to indicate whether substitute sectors have been substituted for defective sectors. The location of the defective sectors is represented, for instance, by the physical sector numbers of the defective sectors. The location of the substitute sectors is represented, for instance, by the physical sector numbers of the substitute sectors.
The status field 220a contains, for instance, a 1-bit flag 220a-1 and a reserved area 220a-2. For example, a value of one in the flag 220a-1 indicates that no substitute sectors have been substituted for defective sectors. A value of zero in the flag 220a-1 indicates that a substitute sector has been substituted for a defective sector.
Although the above-explanations assume that defect management is performed in sector-units, defect management also is known to be performed in block-units, with each block constituted by a plurality of sectors. In such a case, information indicating the location of blocks (called “defective blocks”) containing defective sectors (e.g., the physical sector numbers of the head sectors of the defective blocks) is registered in the SDL instead of information indicating the location of the defective sectors, and information that indicates the location of substitute blocks (for instance, the physical sector numbers of the head sectors of the substitute blocks) is registered instead of information indicating the location of the substitute sectors. For instance, in the case of a DVD, the unit of defect management is an ECC block, i.e. the unit utilized for error correction.
Incidentally, when the number of defective sectors increases, the frequency of substitute sector accesses becomes higher, thereby severely decreasing the speed of recording and reproduction and creating a particularly serious hindrance to the recording and reproduction of moving pictures. In addition, since substitute sectors are secured in the data recording area 95, when numerous substitute areas are secured as a result of increased frequency of substitution, the recordable volume of user data is reduced as well. In such a case, physical reformatting (re-initialization) is recommended after cleaning the disc to remove dirt adhered to the surface of the disc. Subsequently created defects mostly are due to, for example, fingerprints on the disc surface, and most of the subsequently created defects are eliminated by cleaning.
Conventionally, when physical reformatting was performed, all the contents of the status field 220a, field 220b and field 220c in the SDL entry 220 were invalidated
In addition, the conventional technology described in Patent Document 1 relates mostly to DVDs, and in case of BDs, all the contents of the defect list are erased when physical reformatting is carried out.
Patent Document 1: JP 2000-322835A (FIGS. 1A˜1C).
However, in the past, the erasure of the entire contents of the defect list resulted in the following problems.
Namely, because all of the contents of the defect list were erased during physical reformatting, information indicating the location of defective sectors (or sectors where defects could be present) also was lost. Therefore, when there were defects that disc surface cleaning did not eliminate, recording of new data on the disc after formatting could result in user data being recorded despite the possible presence of defects, which required reproduction to be performed for read-modified write. However, reproduction was impossible because of the defects, and, as a result, recording was impossible as well.
In addition, in the past, devices have been known that, after performing physical reformatting, optionally perform defect inspection processing (certification) by checking all the sectors on the disc for the presence of defects and registering information on the discovered defective sectors in a defect list.
As an example of such conventional authentication processing, a technique is known in which authentication data is written over the entire volume space of the disc and the presence of defects on the disc is determined by confirming whether or not the written data can be reproduced correctly. However, the problem with this method is that, in the case of a DVD, for instance, authentication processing requires close to one hour from start to finish, which is extremely inconvenient for the user.
In addition, a type of simplified defect inspection processing called quick certification (Quick Certification) is possible with BDs. During such processing, all the entries in a defect list are inspected for defective clusters, leaving the entries intact when there are defects and invalidating the entries when there are no defects. Therefore, the more entries a defect list has, the longer the processing time becomes, requiring up to 15 minutes or so in the worst case scenario.